1. Field of the Invention
This invention concerns corrosion measurement in general. More specifically it concerns a method and/or apparatus for measuring the rate of corrosion of metallic structures that are subjected to a corrosive ambience.
2. Description of the Prior Art
It has long been known that internal pitting and other forms of accelerated corrosion will result in rapid failure of piping, tanks and other steel structures, all without warning. Heretofore, visual inspection has been the only means of detecting the pitting or other corrosive conditions, and such inspection requires system shut down and disassembly which, or course, is costly and time consuming.
While there is an old U.S. Pat. No. 1,962,168 issued June 12, 1934 to Orin E. Andrus, that patent deals with a lined pressure vessel. It has provision for detecting a leak (if it should occur) through the lining of such a vessel. The arrangement of that patent makes use of the fact that the pressure in the vessel is well above atmospheric. And, if there should be a leak in the lining, the pressure increase would be detected by having small holes that communicate with the space between the high pressure thick wall and the liner within. Clearly, the Andrus patent has no concern for, nor any recognition of a measurement of corrosion. Rather, it intends that any damage to the liner would be detected before the leak could cause extensive injury.
On the other hand, the applicants' invention provides for a thin-walled enclosure that has means for detecting when such thin wall has corroded through. The time element is of concern, so that the rate of corrosion will be detected. The rate detected is based upon a predetermined known thickness of the thin wall, so that the wall of the protected structure will not as yet have been corroded through.